However, at times a large voltage or current value may be required for a particular application. This is typically accomplished using a large capacitor or inductor external to the IC. Commonly, as the voltage and current outputs rise, the respective noise also rises. In addition, as loads to the IC change, the voltage droop may become excessive due to the large voltages and/or currents being provided. Alternatively, fluctuation, or more commonly, “ripple”, in the output current or voltage value may be significant. If the ripple is significant, it can cause errors in the loads supplied with the output voltages or currents. The rate of change of the ripple voltage is the ripple frequency.
One known method of reducing voltage or current ripple is to interleave a number of charge pumps. The number of charge pumps maintains the output voltage or current supply as each charge pump discharges and recharges according to a clock signal. Interleaving requires a number of clock signals to control the firing of the number of charge pumps. The firing of the number of charge pumps may actually increase the voltage ripple as each individual charge pump fires imprecisely due to failure to synchronize the number of clock signals. The management of the number of different clock signals requires a complex control device. Furthermore, the additional clock inputs and related connections also consume additional real estate on the IC, which increases cost as well as makes for a larger IC. Also, interleaving may not provide a large voltage or current that may be needed by a particular circuit application or configuration.
Accordingly, there is a need for a charge pump configuration that supplies large voltage or current without the complex control and multitude of inputs of an interleaved solution.